CVE-2023-36556
📋 TL;DR
This CVE describes an incorrect authorization vulnerability in FortiMail webmail that allows authenticated attackers to log into other users' accounts within the same web domain via crafted HTTP/HTTPS requests. The vulnerability affects FortiMail webmail versions 7.2.0-7.2.2, 7.0.0-7.0.5, and versions below 6.4.7. Attackers can potentially access sensitive email data and impersonate legitimate users.
💻 Affected Systems
- FortiMail webmail
📦 What is this software?
Fortimail by Fortinet
Fortimail by Fortinet
Fortimail by Fortinet
Fortimail by Fortinet
Fortimail by Fortinet
Fortimail by Fortinet
Fortimail by Fortinet
⚠️ Risk & Real-World Impact
Worst Case
Complete compromise of all user accounts within the same web domain, leading to data exfiltration, privilege escalation, and unauthorized access to sensitive communications.
Likely Case
Targeted account takeover allowing attackers to read emails, send messages as legitimate users, and potentially access other integrated systems.
If Mitigated
Limited impact with proper network segmentation, strong authentication controls, and monitoring for unusual login patterns.
🎯 Exploit Status
Requires authenticated access but exploitation appears straightforward based on vulnerability description. No public exploit code identified at time of analysis.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 7.2.3, 7.0.6, 6.4.7 and above
Vendor Advisory: https://fortiguard.com/psirt/FG-IR-23-202
Restart Required: Yes
Instructions:
1. Download appropriate patch version from Fortinet support portal. 2. Backup current configuration. 3. Apply firmware update via FortiMail web interface or CLI. 4. Reboot system. 5. Verify version update and functionality.
🔧 Temporary Workarounds
Restrict webmail access
allLimit webmail access to trusted networks using firewall rules or VPN requirements
Enable multi-factor authentication
allImplement MFA to add additional protection layer even if account takeover occurs
🧯 If You Can't Patch
- Implement strict network segmentation to isolate FortiMail systems from untrusted networks
- Enable detailed logging and monitoring for unusual login patterns or account access
🔍 How to Verify
Check if Vulnerable:
Check FortiMail version via web interface (System > Status) or CLI command 'get system status'Check Version:
get system status | grep VersionVerify Fix Applied:
Verify version is 7.2.3+, 7.0.6+, or 6.4.7+ after patch application📡 Detection & Monitoring
Log Indicators:
- Multiple successful logins from same source IP to different user accounts
- Unusual login times or locations for specific users
- Failed authorization attempts followed by successful logins to different accounts
Network Indicators:
- HTTP/HTTPS requests with manipulated session or authentication parameters
- Unusual patterns of account switching within short timeframes
SIEM Query:
source="fortimail" AND (event_type="login" OR event_type="authentication") | stats count by src_ip, user | where count > threshold